In work on globally-scheduled real-time multiprocessor systems, analysis is lacking for supporting real-time applications developed using general processing graph models. In this paper, it is shown that bounded deadline tardiness can be ensured for such applications on a multiprocessor with no utilization loss. This result is general: it is applicable to periodic, sporadic, and rate-based directed...
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As multicore platforms become ever larger, overhead-related factors play a greater role in determining which real-time scheduling algorithms are preferable. In this paper, such factors are investigated through an empirical comparison of global, partitioned, and clustered EDF scheduling algorithms on a 24-core Intel system. On this platform, global EDF proved to be a non-viable choice for hard real...
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LLF (Least Laxity First) scheduling, which assigns a higher priority to a task with smaller laxity, has been known as an optimal preemptive scheduling algorithm on a single processor platform. However, its characteristics upon multiprocessor platforms have been little studied until now. Orthogonally, it has remained open how to efficiently schedule general task systems, including constrained deadl...
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We present a new approach to decrease task preemptions and migrations in optimal global real-time schedules on symmetric multiprocessors. Contrary to classical approaches, our method proceeds in two steps, one off-line to place jobs on intervals and one on-line to schedule them dynamically inside each interval. We propose a new linear programming formulation and a local scheduler which exhibits lo...
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When locking protocols are used in real-time systems, bounds on blocking times are required when ensuring timing constraints. While the term “blocking” is well-understood in the context of uniprocessor real-time systems, the same is not true in the multiprocessor case. In this paper, two definitions of blocking are presented that are applicable to suspension-based multiprocessor lock...
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This paper presents a new schedulability analysis for hierarchically scheduled real-time systems executing on a single processor using SIRAP, a synchronization protocol for inter subsystem task synchronization. We show that it is possible to bound the number of self-blocking occurrences that should be taken into consideration in the schedulability analysis of subsystems. Correspondingly, we presen...
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This paper is concerned with the development of reliable real-time systems for use in high integrity applications. It advocates the use of diverse replicated channels, but does not require the dependencies between the channels to be evaluated. Rather it develops and extends the approach of Little wood and Rush by (for general systems) by investigating a two channel system in which one channel, A, ...
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The problem of modeling and controlling resources in a system with interaction between hardware and software is considered. A model encompassing both hardware and software dynamics is developed together with an on-line estimation scheme in order reduce dependence on apriori information. A control structure is presented in order to control performance under constrained resource situations and to re...
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Time-triggered periodic control implementations are over provisioned for many execution scenarios in which the states of the controlled plants are close to equilibrium. To address this inefficient use of computation resources, researchers have proposed self-triggered control approaches in which the control task computes its execution deadline at runtime based on the state and dynamical properties ...
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We propose a system-level design flow for building automation and control (BAC) systems. The input to the design flow is a high level description of the control algorithms given in a model-based environment such as Simulink. The input specification is translated into an intermediate format, and then automatically refined into a distributed implementation. Refinement includes optimal mapping of the...
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Recent years have seen the growing deployments of Cyber-Physical Systems (CPSs) in many mission-critical applications such as security, civil infrastructure, and transportation. These applications often impose stringent requirements on system sensing fidelity and timeliness. However, existing approaches treat these two concerns in isolation and hence are not suitable for CPSs where system fidelity...
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The emerging wireless charging technology is a promising alternative to address the power constraint problem in sensor networks. Comparing to existing approaches, this technology can replenish energy in a more controllable manner and does not require accurate location of or physical alignment to sensor nodes. However, little work has been reported on designing and implementing a wireless charging ...
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We examine optimal strategies for querying a sensor network when energy efficiency and data freshness need to be balanced. We use statistical information about the nature of events monitored by the sensor network to develop good query schedules. For Poisson event arrivals, we develop an optimal scheduling strategy that is actually a periodic querying policy. For hyper exponential distribution of e...
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WirelessHART is an open wireless sensor-actuator network standard for industrial process monitoring and control that requires real-time data communication between sensor and actuator devices. Salient features of a WirelessHART network include a centralized network management architecture, multi-channel TDMA transmission, redundant routes, and avoidance of spatial reuse of channels for enhanced rel...
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Extending the lifetime of wireless sensor networks requires energy-conserving operations such as duty-cycling. However, such operations may impact the effectiveness of high fidelity real-time sensing tasks, such as object tracking, which require high accuracy and short response times. In this paper, we quantify the influence of different duty-cycle schemes on the efficiency of bearings-only object...
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Formal models used for representing recurrent real-time processes have traditionally been characterized with a period parameter that specifies the minimum amount of time that may elapse between successive invocations of the process. However a recently proposed model called the non-cyclic GMF model has the distinctive feature that there need be no single period parameter characterizing the recurren...
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